How Does a Water Softener Work?

A water softener removes hardness. The US Geological Survey defines hardness simply as "the amount of dissolved calcium and magnesium in the water," and the EPA says cation exchange softeners "remove the calcium and magnesium ions found in hard water."

Taking those minerals out matters for what they leave behind. The EPA says homes with significant hardness "may see mineral/scale formation on plumbing fixtures and appliances and find it difficult to get sufficient lather from soaps and detergents." In a 2009 Battelle study funded by the Water Quality Research Foundation, low-flow showerheads and faucets on unsoftened water clogged in less than seven days of accelerated testing, while the units on softened water made it through without problems.

Hardness itself is "not a health concern, but it can be a nuisance," according to the USGS. A softener treats hardness. It is not a drinking water filter. Cleaner, better-tasting water at the kitchen sink is a job for reverse osmosis.

Regeneration is how a softener recharges itself. The resin can only hold so many hardness minerals. As the Illinois State Water Survey puts it, "When the sodium is depleted, the resin needs to be regenerated."

During regeneration:

1. The softener draws salt water from the brine tank.
2. The brine is washed through the resin. The high levels of sodium or potassium force the calcium and magnesium off the beads, according to the City of Woodland.
3. The hardness minerals and leftover brine are flushed down the drain, and the resin is ready to soften water again.

This is why a salt-based softener needs salt. The salt in the brine tank is what puts sodium back on the resin.

Most water softeners regenerate every few days, according to Angi. Some regenerate as often as several times a day, and some only every two weeks. Three things set the pace, per Angi:

• How hard your water is. "Water with higher mineral content will trigger more frequent regenerations."
• How much water your home uses. More water through the softener fills the resin faster.
• The size of the tank. "Larger tanks can go longer between cycles."

How the softener decides also matters. The EPA says softeners that use demand-initiated regeneration, which regenerate based on actual water use, "are more efficient than water softeners that function based on a fixed schedule." In a 2010 WaterSense notice on softeners, the EPA noted that some units regenerate well before their capacity is reached and "may waste additional water regenerating more frequently than is necessary."

Regeneration takes about 70 to 120 minutes, according to Angi.

Softeners are usually set to regenerate in the middle of the night. The City of Woodland explains why: "soft water is not available during the regeneration."

Regeneration also uses water. The EPA's WaterSense program points to a voluntary efficiency rating in the NSF/ANSI 44 standard that requires softeners to use 5.0 gallons of water or less per 1,000 grains of hardness removed. A demand-initiated softener sized for your home keeps that water and salt use down.

HomeGuide says quality water softeners last 15 to 20 years with proper maintenance. Angi puts the range at 10 to 25 years, with an ion-exchange softener lasting 15 years on average.

What shortens or extends that life:

• Water hardness and use. HomeGuide says lifespan "depends on the water quality and hardness, water usage, the system quality, and the maintenance frequency." Angi notes that in homes with harder water, a softener runs and regenerates more often, which "leads to more wear and tear."
• Sizing. "Undersized systems regenerate more frequently, increasing salt usage and reducing the system's lifespan," according to HomeGuide.
• Maintenance. HomeGuide recommends cleaning the brine tank and checking salt levels. Angi adds flushing the resin bed once a year.

Signs a softener may be failing, according to Angi, include trouble getting soap to lather, crusty scale returning on fixtures, more spots on glassware and dishes, and hearing the softener run continuously.

Hardness is measured in grains per gallon (gpg). The Water Quality Association calls 7 to 10.5 gpg hard and anything above 10.5 very hard. Here is what local utilities report:

Fort Worth says its water "is usually hard enough to create a coating on the inside of any metal pipes or fixtures." The North Texas Municipal Water District notes that hardness "may be higher or lower at different times of the year."

What we measure at the tap can run higher than the utility reports. In homes we have tested in Frisco, McKinney, Prosper, Celina, and Forney, we have measured 11 to 16 grains per gallon or more, which is hard to very hard.

Harder water means the resin fills faster and the softener regenerates more often. That is why the right size of softener depends on your actual number, not the city average.

The only way to know your number is to test the water at your tap. Hardness varies by city, by season, and from what the utility reports to what reaches your home.

TAC offers a free in-home water test across Dallas-Fort Worth. We test your water, tell you how hard it is, and give you a recommendation for your home before you decide anything.